The biggest obstacle was the controls. I've only ever played Smash with a GameCube controller, which is super different than the 3DS. Giving the buttons different shapes makes a big difference in how your hand aligns to it.
I ended up reconfiguring the controls to:
I think this scheme works for me because I've been playing a lot of Super Mario World recently, and SMW uses B for jump ("A"), Y for dash ("B"), and A for spin jump ("X"). (It also matches the controls for Smash Bros. 64, which is where I got the idea for the scheme.)